Electric circuit breaker



A118 22, 1950 w. G. BOURNE 2,519,629

ELECTRIC CIRCUIT BREAKER Filed Nov. 6, l94 7 2 Sheets-Sheet l u8 22, 1950 w. G. BOURNE 2,519,529

ELECTRIC CIRCUIT BREAKER Filed Nov. 6, 1947 2 Sheets-Sheet 2 la?) @mlb ZJ-, 6,50 W12/e f/f f4* @WQ Patented Aug. 22, 1950 ELECTRIC ICIRCUIT BREAKER William George Bourne, London, England, assignor to Rotax Limited, London, England Application November 6, 1947, Serial No. 784,357 In Great Britain October 30, 1945 Sectionl, Public Law 690, Augiist`8', 1946 Patent expires October 30, 1966 Claims. l

This invention relates to electric circuit break*- ers, and has for its object to enable a small breallzer responsive to the heating action ci an electric current to be provided in a simple and compact form. I y

The invention comprises the combination ci a spring loaded snapeactionlever mechanism carry-y ing a Contact and operableby either of a pair of push buttons, and a complementary contact carried by a thermally deformable member, the arrangement being such that the mechanismis also able to be actuated for' separation of the contacts by deformation of the said member.

The invention further cor'rimises' the combination with a circuit breaker as speciiied in the preceding paragraph, oian additional pair of contacts arranged to be closed by actuation of one oi the 'push buttons for short-circuiting at least part of the breaker tol render the thermally deformable member inoperative.

ln the accompanying drawings:

Figure l is a side elevation of an electric circuit breaker responsive to' the heating action of an excess current constructed in accordance with the invention.

Figure 2 is a horizontal section taken on' the line of Figure 1'. Y l v Figure 3' is a vertical section taken on the line of Figure l.

n one convenient embodiment of the invention as illustrated in the drawings, there is' provided a hollovv body part or frame i which is preferably made as a moulding from insulating material. Within the' body part is' mounted a sheet metal frame 2, and on this frame is carried a bowed spring metal strip 3* having one end pivotally anchored to' one end oi the frame 2 at 4. '"Ihe other end of the spring strip 3 is arranged to eX- tend beyond a second pivotal anchorage on the frame provided by a bent strip 5 supported from a transverse pin 'd and having a forked end 'I Which engages a pair of shoulders formed by cutting away' side portions from the extreme end oi the strip Adjacent to this Second anchorage there is provided on the frame a pivot pin 8 which supports a contact lever 9 carrying one of the contacts iii. A coiled spring I I on the pin 8 has one end in engagement with the lever 9 and the other in engagement with a part I2 of the frame 2. The lever 9 also has a bent up portion I3 adjacent to the contact II) which is adapted to engage a part of the bowed strip 3 between its anchorages. Further there is arranged in the body part I adjacent to the extended end oi the bowed strip a coiled spring i4 having an integral (Cl. 20G-122) arm l5 projecting from one of its ends. Aiternatively a spring loaded pivoted ar'ni may be provided. The' free end of the arm I5 is arranged to act on one side of the extended end of the bowed strip 3 and is' movable by a push-button I6` which forms one' of a pair slidably mounted in thev iront of the body part I (i. e. the top part as seen in` Figure 1). The second push button I 1 is loaded by a spring I8 and is arranged to act on a part of the strip 3` between the anchorages thereof, through the medium of the horizontal portion I9 of a lever 20 comprising a pair of parallel side portions pivotally mounted in the frame at 2|. The bowed strip 3 is so arranged that its curvature is reversed when. it is pushed through a central position from one limit to another. It is movable in one direction by the push button Il' and in the other direction either by the contact lever 9 or by the arm I5 associated with the pushbutton i6. One ci ther limit positions of the strip is determinec'l by the abutment member 5 which is adjustabie bymeans of the screw 22. An extension 23 of the frame 2 which passes to the exterior ofY the body part I has secured to it a terminal piece 231.

Within the body part and alongside the contact lever 9 is mounted a flat bi-metal strip 24 which is secured at one end to the body part and at its free end carries the complementary contact 25. This strip is connected to another terminal 26 on the exterior oi the body part. The required thermal deformation of t e oi-metal strip may be' eiiected by the heating action of the current passing through it when the contacts are closed, but preferably a separate heating element is employed. This latter may consist of a resistance oi any convenient form, but preferably it consists of a iiat plate of metal 21 formed with parallel slots in staggered relation, the plate being mounted as shown in the body part adjacent to the side of the 1oi-metal strip 24 remote from the contact lever 9, and being connected in line with the bi-'metal strip. Also at one side of the bi-metal strip 24 there is provided in the body part an adjustable abutment screw 28.

The arrangement is such that closing of the contacts I0, 25 is eiiected by the action of the push button II on the portion of the bowed strip 3 lying between the anchorages. This has the eiect of reversing the curvature of the strip, causing it to assume the position shown by broken lines in Figure l, and rocking the contact lever 9. Separation of the contacts is effected by the push-button I6 through the action of the arm I5 on the extended end of the 3? bowed strip 3, causing the deflection of this strip to be again reversed so that it returns to the upper position as seen in Figure 1.

So long as the current passing through the breaker is normal the heat generated in the heating element 21 and in the bi-metal strip 24 is ineiective, but an abnormal or excess current results in the bi-metal strip being deflected, and the pressure thereby exerted by this strip on the contact lever 9 causes the latter to actuate the bowed strip through the medium of the bent up portion I3 on the said lever and effect the sudden separation of the contacts.

For some purposes it is desirable to be able to reclose the contacts and hold them closed while an overload persists. To meet this requirement there are provided an additional pair of contacts which serve to short circuit the bimetal strip or its associated heating element.

In the arrangement shown a resilient metal the button I'I is actuated for closing the breaker, f

a slight additional movement brings the longer side of the said lever into engagement with the blade 29 and closes the contacts 30 and 3l so short circuiting the breaker, this condition being maintained so long as the additional contacts are held closed. On releasing the button l1 it returns suiciently to allow the additional contacts to separate and so restore the normal working conditions of the breaker.

By this invention I am able to provide a small circuit breaker responsive to the heating action of an excess current in a very simple and compact form. The invention is not, however, restricted to the example described, as subordinate constructional details may be varied to suit dii-ferent requirements.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. An electric circuit breaker comprising in combination a pair of complementary contacts, an over-centre spring, a thermally deformable member carrying one of said contacts, a lever carrying the other of said contacts and responsive to opposite movements of said spring for opening and closing said contacts, a pair of push buttons arranged to act on said spring at difierent positions for causing opposite movements of said spring past a dead-centre position, and means whereby movement imparted to said lever through said contacts in response to deformation of said thermally deformable member can serve to move said spring in the direction for causing said contacts to open.

2. An electric circuit breaker comprising in combination a pair of complementary contacts, a bowed over-centre spring, a thermally deformable bi-metal strip carrying one of said contacts, a lever carrying the other of said contacts and responsive to opposite movements of said spring for opening and closing said contacts, a pair of push buttons arranged to act on the same side of said spring at different positions for causing opposite movements of said spring past a dead centre position, and means whereby movement imparted to said lever through said contacts in response to deformation of said bi-metal strip can serve to move said spring in the direction for causing said contacts to open.

3. An electric circuit breaker comprising in combination a pair of complementary contacts, a bowed over-centre spring, Xed and adjustable anchorages supporting said spring at positions spaced apart, a thermally deformable bi-metal strip carrying one of said contacts, a lever carrying the other of said contacts and responsive to opposite movements of said spring for opening and closing said contacts, a pair of push buttons arranged to act on the same side of said spring at diierent positions for causing opposite movements of said spring past a dead centre position, and means whereby movement imparted to said lever through said contacts in response to deformation of said bi-metal strip can serve to move said spring in the direction for causing said contacts to open.

4. An electric circuit breaker as claimed in claim 1 and having an additional pair of contacts arranged to be closed by movement of one of said push buttons beyond its normal operating position for short-circuiting at least a part of the breaker to render said thermally deformable member inoperative.

5. An electric circuit breaker as claimed in claim 1 and having a second lever through which one of said push buttons acts on said spring, an additional pair of contacts, and a spring blade carrying one of said additional pair of contacts, said blade being movable by said second lever in response to movement of the corresponding push button beyond its normal operating position, for short-circuiting at least a part of the breaker to render said thermally deformable member inoperative while the first mentioned contacts are closed.

WILIJAM GEORGE BOURNE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,315,466 Cavanagh Sept. 9, 1919 1,853,957 Brotz Apr. 12, 1932 2,420,300 Cataldo et al. May 13, 194'? 

